Three weeks ago a remarkable caravan of vehicles arrived at the Mexican town of Reynosa, just across the border from Hidalgo, Texas. It left the northern border of Nicaragua on 12 October, carrying the relatives of migrants who made the journey north to cross illegally into the United States, but vanished along the way. The caravan, which finished its journey through Central America this weekend, was trying to draw attention to their disappearance and – if possible – find them.

Teodora Ñaméndiz last saw her son in 1980 and hadn’t heard from him for 27 years. It turns out he never reached the US border. In Mexico he became an alcoholic, and when he stopped receiving letters thought his family had rejected him. Now they have been reunited through investigations carried out by the Movimiento Migrante Mesoamericano, which organised the caravan.

Of the estimated 20,000 Central American migrants who disappear each year, many are kidnapped or killed. In Mexico alone, some 70,000 are thought to have disappeared since 2006. Amnesty International recently called on the authorities to end the impunity of officials acting in collusion with gang leaders who are known to capture and torture migrants, hoping to extract ransoms.

Official indifference is mitigated by charities and voluntary groups. When the caravan stopped in Cordoba in the state of Veracruz, the mothers were received by a group of local women from La Patrona, which provides food and water to the hundreds of migrants who hitch rides on the top of the train heading north through Mexico to the border cities. The train is known as La Bestia because so many people are injured or killed trying to ride its freight cars.

One of the women from La Patrona, Norma Romero, has explained how they began 17 years ago:

One day my sisters and I came to the train tracks early after having bought bread and milk. The train was going by and we couldn’t cross. While we were waiting, those on the train called out to us: ‘Mothers, we are hungry; give us your bread; give us your milk.’ … We asked ourselves where they were from with such a different accent… We organised ourselves and we began with 30 rations that we threw up to those who were on the train – bags with beans, tortilla and water.

Now 14 women prepare daily packets of food and water. Many migrants take nothing with them for the 3000 km train journey through Mexico, knowing that if they did, it would only be stolen.